Pressure sensitive sealant composition and method of sealing by using same

ABSTRACT

The invention relates to a pressure sensitive sealant composition for sealing a clearance between a lamp unit housing and a vehicle body panel of an automotive vehicle. The pressure sensitive sealant composition includes (a) 10-40 wt % of a component A that is at least one copolymer selected from the group consisting of hydrogenated styrene-butadiene copolymers, hydrogenated styrene-isoprene copolymers, and modified copolymers thereof; (b) a component B that is at least one tackifier selected from the group consisting of petroleum resins, terpene resins, rosin resins, coumarone-indene resins, hydrogenated resins thereof, and modified resins thereof, and (c) a component C that is a hydrocarbonic plasticizer. The pressure sensitive sealant composition is prepared by maxing together 100 parts by weight of the component A, 20-60 parts by weight of said component B, and 150-400 parts by weight of said component C. In order to apply the pressure sensitive sealant composition for the purpose of saealing, the pressure sensitive sealant composition is heated end directly applied in the state of a bead onto a member to be sealed, or otherwise applied to the member after it has been formed into the bead state.

BACKGROUND OF THE INVENTION

This invention relates to a pressure sensitive sealant composition and amethod for sealing by using the sealant composition, and moreparticularly to the sealant composition which is used in a clearancebetween a rear combination lamp unit and a vehicle body of an automotivevehicle and provided with improved watertight seal under environmentalcondition where the vehicle is used, improved operational efficiency forrepairing and disassembly of the lamp unit, and improved removalcharacteristics allowing the sealant composition to be peeled of in aninterfacial breaking condition, and the sealing method by use thesealant composition.

In an assembly process of a modern automotive vehicle, lamp (light)unite such as rear combination lamp units are installed to a vehiclebody which has been painted, at a trimming step. At this time, a varietyof sealing materials are used in a clearance between each lamp unit andthe vehicle body for the purpose of obtaining water-tight sealtherebetween. In general, a molded gasket or a butyl rubber basedadhesive is used as the sealing material The molded gasket is usuallyformed by punching out a sheet formed of closed cell-type foam rubber orplastic, and the butyl rubber based adhesive is usually applied uponheating at a temperature not lower than 100° C.

SUMMARY OF THE INVENTION

Concerning the molded gasket, it has been previously formed by punchingout the above sheet into a shape corresponding to a portion requiring awater-tight seal on the side of a housing of the rear combination lampunit. The thus formed molded gasket is assembled in the seal requiredportion on the side of the rear combination lamp unit housing. Thismolded gasket exhibits its water-tight seal under the effect ofresilience generated upon compression or when compressingly put betweenthe rear combination lamp unit housing and the vehicle body panel byengaging small screws provided on the side of the rear combination lampunit housing. More specifically, the molded gasket is usually formed bypunching out the sheet of the closed cell-type foam material by using ametallic die or a so called Thomson blade. The foam material is made ofrubber (such as EPDM=copolymer of ethylene, propylene and diene),polyurethane resin, silicone resin or the like, and has been foamed tohave a volume of 3 to 5 times that in its not-foamed state. In such acase, the molded gasket is used upon being compressed 25 to 50% indirection of thickness thereof when the rear combination lamp unit isassembled in the vehicle body, in order to obtain necessary resiliencefor the purpose of securing a water-tight seal between the rearcombination lamp unit housing and the vehicle body panel.

However, under environmental conditions where automotive vehicles areused, the above molded gasket employed in a compressed state will besubjected to permanent deformation due to its deterioration caused byheat and/or humidity upon long time use. This relatively lowers theresilience of the molded gasket and therefore degrades water-tight seal.With this, water penetrates into, for example, a trunk compartment ofthe vehicle. Furthermore, such a molded gasket is not necessarilysufficient in follow-up characteristics to polyvinyl chloride-basedsealant applied at a plurality of step sections having a step-height ofabout 1 mm in the vehicle body panel, for example, at a so-called zerojoggle joint section between a rear fender panel and a rear panel, eachsection requiring water-tight seal. When the rear combination lamp unitis assembled in the vehicle body having such a surface structure,water-tight seal between the rear combination lamp unit and the vehiclebody becomes insufficient thereby causing, for example, water leak intothe trunk compartment of the vehicle.

Concerning the butyl rubber-based adhesive, it is first heated at atemperature of not lower than 100° C., and then applied on the surfaceof the housing of the rear combination lamp unit, following the shape ofa section requiring watertight seal. Such a butyl rubber-based adhesivecan exhibit water-tight seal between the rear combination lamp unit andthe vehicle body under a high adhesiveness to the plastic surface of therear combination lamp unit housing and to the painted surface of thevehicle body panel, not under resilience generated upon compression asin the molded gasket. Besides, the butyl rubber-based adhesive isusually applied at the temperature of not lower than 100° C. along theshape of a groove formed on the surface of the tear combination lampunit housing in such a manner as to take the state of a bead having across-sectional diameter ranging from 8 to 12 mm. Thus, the butylrubber-based adhesive can provide water-tight seal in an interfacialregion between the rear combination lamp unit housing and the vehiclebody panel under the action of the high adhesiveness against the surfaceof the lamp unit housing and the surface of the vehicle body panel.

In general, the butyl rubber-based adhesive has such a characteristicthat stress can be reduced immediately after compression and thereforeit does not have resilience. Accordingly the butyl rubber-based adhesivedoes not make its decomposition and permanent deformation in thedirection of thickness, owing to its deterioration upon being subjectedto heat and humidity for a long time in the environmental conditionswhere automotive vehicles are used. Additionally, the butyl rubber-basedadhesive can be smoothly reduced in stress immediately aftercompression, and therefore is sufficient in follow-up characteristics tostep sections having a step-height of around 1 mm in the vehicle bodypanel at a section requiring water-tight seal. Thus, the butylrubber-based adhesive is not problematic from the viewpoint ofreliability for water-tight seal.

However, the butyl rubber-based adhesive is high in adhesiveness, andtherefore a edge section of the rear combination lamp unit is requiredto be broken open by a plastic bar or the like while it is graduallyheated by an industrial dryer or the like, for the purpose ofdisassembling the rear combination lamp unit when the rear combinationlamp unit is replaced with a new one in an automotive vehicle servicefactory or the like. Such operations are very troublesome. Additionally,when the rear combination lamp unit is disassembled, the butylrubber-based adhesive make its breaking (cohesive breaking) whileleasing remains of the butyl rubber-based adhesive on the both surfacesof the vehicle body panel and of the rear combination lamp unit housing.Accordingly, in case that the new rear combination lamp unit with newbutyl rubber-based adhesive is re-assembled in the vehicle body, it isrequired to manually remove the remains of the adhesive containing alarge amount of dust, dirt and oil, left on the surface of the vehiclebody panel, in order to secure water-tight seal after re-assembly of thenew rear combination lamp unit. Such operations require a long time anda considerable labor. Besides, there is the fear that the butylrubber-based adhesive adhered to the hands of an operator again adheresonto the painted surface of the vehicle body and to interior trims ofthe vehicle, thereby degrading the external appearance of the vehicleafter the displacement operations for the rear combination lamp unit.

Further, when the vehicle is dismantled or scrapped, it is substantiallyimpossible to recover and recycle the plastic materials (mainlypolypropylene resin) of the rear combination lamp unit housing becauseit is very difficult to remove the butyl rubber-based adhesive which hasbeen adhered deeply to the bottom surface of the grove formed on therear combination lamp unit housing.

In view of the above drawbacks encountered in conventional techniques,the inventors have conducted researches and developments and found thata pressure sensitive sealant composition having a particular compositioncan effectively solve the conventional drawbacks, thereby reaching thepresent invention.

It is an object of the present invention to provide an improved pressuresensitive sealant composition and an improved sealing method, which canprovide excellent water-tight while allowing the pressure sensitivesealant composition to be easily removable from a base member to whichthe sealant composition has been applied.

Another object of the present invention is to provide an improvedpressure sensitive sealant composition and an improved sealing method,which can be effectively used in and for a clearance between a rearcombination lamp unit and a vehicle body panel of an automotive vehicle,thereby exhibiting excellent water-tight seal and high operationalefficiency for repairing and disassembly of the lamp unit, whilepreventing remains of the pressure sensitive sealant composition frombeing left on the surfaces of the rear combination lamp unit housing andthe vehicle body panel.

An aspect of the present invention resides in a pressure sensitivesealant composition which comprises (a) 10-40 wt % of a component A thatis at least one copolymer selected from the group consisting ofhydrogenated styrene-butadiene copolymers, hydrogenated styrene-isoprenecopolymers, and modified copolymers thereof; (b) a component B that isat least one tackifier selected from the group consisting of petroleumresins, terpene resins, rosin resins, coumarone-indene resins,hydrogenated resins thereof, and modified resins thereof: and (c) acomponent C that is a hydrocarbonic plasticizer, wherein said pressuresensitive sealant composition is prepared by mixing together 100 partsby weight of said component A, 20-60 parts by weight of said componentB, and 150-400 parts by weight of said component C.

Another aspect of the present invention resides in a method for sealinga member, which comprises (a) preparing the pressure sensitive sealantcomposition; (b) heating the pressure sensitive sealant composition; and(c) applying the heated pressure sensitive sealant composition to themember.

A further aspect of the present invention resides in a method forsealing a member, which comprises (a) preparing the pressure sensitivesealant composition; (b) forming the pressure sensitive sealantcomposition into a predetermined shape; and (c) applying the pressuresensitive sealant composition of the predetermined shape to the member.

DETAILED DESCRIPTION OF THE INVENTION

As stated above, a pressure sensitive sealant composition according tothe present invention comprises the component A that is at least onecopolymer selected from the group consisting of hydrogenatedstyrene-butadiene copolymers (HSB), hydrogenated styrene-isoprenecopolymers (HSI), and modified copolymers thereof. These modifiedcopolymers are referred to, for example, as those prepared byintroducing polar groups, such as carboxyl groups and hydroxyl groups,into HSB and HSI. The content of the component A in the pressuresensitive sealant composition is 10-40 wt %. If it is less than 10 wt %,the pressure sensitive sealant composition becomes inferior in weatherability and removability from a vehicle body panel upon disassembly of arear combination lamp unit. If it is greater than 40 wt %, the pressuresensitive sealant composition becomes insufficient in adhesion.Furthermore, it becomes difficult to maintain the workability indischarging the pressure sensitive sealant composition from a nozzle dueto the increase of its melt viscosity.

The pressure sensitive sealant composition further comprises a componentB that is at least one tackifier selected from the group consisting ofpetroleum resins, terpene resins, rosin resins, coumarone-indene resins,hydrogenated resins thereof, and modified resins thereof. Of these,hydrogenated petroleum resins and modified terpene resins areparticularly preferably used. The content of the component B in thepressure sensitive sealant composition is in a range of 20-60 parts byweight relative to 100 parts by weight of the component A. If it is inthis range, it becomes possible to maintain a good balance betweensealing property (adhesion) of the sealant composition and removabilityof the sealant composition. If it is less than 20 parts by weight, itbecomes difficult to have a sufficient adhesion of the sealantcomposition. If it is greater than 60 parts by weight, it becomesdifficult to disassemble a rear lamp unit and to remove the sealantcomposition.

The pressure sensitive sealant composition further comprises a componentC that is a hydrocarbonic plasticizer. This hydrocarbonic plasticizermay be selected from various conventional and commercial products ofhydrocarbonic plasticizer. Its preferable examples are liquid paraffinand polybutene and liquid polybutadiene. The content of the component Cin the pressure sensitive sealant composition is in a range of 150-400parts by weight relative to 100 parts by weight of the component A. Ifit is less than 150 parts by weight, the sealant composition becomesinferior in adhesion. Furthermore, it becomes difficult to maintain theworkability in discharging the pressure sensitive sealant compositionfrom a nozzle due to the increase of its melt viscosity. If it isgreater than 400 parts by weight, it becomes difficult to disassemble arear lamp unit and to remove the sealant composition. Furthermore, theheat resistant flow temperature becomes too low.

Besides the above-mentioned components A, B and C, the pressuresensitive sealant composition may optionally comprise at least oneadditive such as wax, filler, and antioxidant. The content of the atleast one additive in the sealant composition is preferably 5-40 wt %,from the viewpoints of (1) the formation of the sealant composition intostate of a bead and (2) the workability in discharging the pressuresensitive sealant composition from a nozzle. Preferable examples of thewax are paraffin wax, microcrystalline wax, Fisher-Tropsh wax, lowermolecular weight polyethylene, lower molecular weight polypropylene,atactic polypropylene, and modified products of these. Preferableexamples of the filler are calcium carbonate, barium sulfate, talc,clay, titanium oxide, carbon black, white carbon, glass balloon.Examples of the antioxidant are hindered phenol antioxidant and hinderedamine antioxidant.

It is preferable that the pressure sensitive sealant composition has a180° angle peel strength ranging from 10 to 50 N/25 mm. When its 180°angle peel strength is in this range, it becomes possible to easilydetach a sealed end portion of a rear combination lamp housing from avehicle body panel by a plastic bar or by hand and then to completelyremove the lamp housing from the vehicle body panel by making aninterfacial breaking of the sealant composition by hand. The 180° anglepeel strength may be measured as follows: First, a laminate is prepared.This laminate has (1) a polyester film (thickness: 100 μm), (2) a layerof the pressure sensitive sealant composition attached to the polyesterfilm, and (3) a removable paper attached to the sealant compositionlayer. Then, a portion of the removable paper is peeled off from thesealant composition layer. After that, the resultant exposed portion ofthe sealant composition layer is attached to a first portion of apainted sheet by adding a load of 4 kgf using a roller, thereby toprepare a specimen. Then, the specimen is allowed to stand still for 24hr at room temperature Then, the specimen is set in a tensile tester, inwhich only a second portion of the painted sheet and only the laminateare respectively grasped by upper and lower grasping devices. In such aset state, these are pulled in opposite directions (or in directionsdifferent an angle of 180°) through the upper and lower grasping devicesat a speed of 50 mm/min. An Autograph DSS*500 model (trade name)produced by Shimadzu Corporation may be used as the tensile tester.

The pressure sensitive sealant composition of the present invention canbe prepared by supplying the above-discussed components A, B and C, andadditives such as other fillers and antioxidants, if necessary, into akneader whose temperature is set at a level at which the abovecomponents and the additives melt; and then by sufficiently melt andmixing the content of the kneader. Examples of the kneader are aHenschel mixer, a Brabender type kneader, and a disperser which areprovided with a heating device and defoaming device. The inside of thekneader is at a reduced pressure, if necessary, in which the content(mixed substances) of the kneader is stirred until it becomeshomogeneous. The thus obtained pressure sensitive sealant composition isfilled and stored in a pail or a drum.

Hereinafter, a method of sealing with a sealant of the above-discussedpressure sensitive sealant composition will be discussed. The basemember to be sealed with the sealant is not limited to a particular one;however, the pressure sensitive sealant composition of the presentinvention is effectively used as the sealant particularly in case thatthe base member is a housing of the rear combination lamp (light) unit,or a vehicle body panel of an automotive vehicle. Discussion will bemade on such a case.

As an example, the pressure sensitive sealant composition of the presentinvention is applied under heating in and along a rib-groove formed onthe housing of the rear combination lamp unit of the automotive vehicle,in the state of a generally round bead having a cross-sectionaldiameter, for example, ranging from 8 to 12 mm. More specifically, thepressure sensitive sealant composition stored in the pail or the drum isapplied on the surface of the housing of the rear combination lamp unit,for example, by using a heating and applicating apparatus generallycalled a bulk melter. The bulk melter is arranged such that its casingplate is heated at a temperature not lower than 100° C., preferably atabout 150° C., so that only the pressure sensitive sealant compositionlocated immediately under the casing plate is molten, upon which thesealing composition is sucked up by a constant flow rate gear pump orthe like, so as to be applied onto the surface of the housing of therear combination lamp unit through an applying device having theapplication nozzle.

It is usual that the pressure sensitive sealant composition is heatedand applied in the state of the bead onto the surface of the base member(to be sealed) such as the rear combination lamp unit housing, bydischarging. However, as far as sufficient water-tight seal can beensured, the bead of the pressure sensitive sealant composition may takethe cross-sectional shape of oval or triangle, or other differentcross-sectional shapes (such as an asymmetrical cross-sectional shaperelative to a line passing through the center of the cross-section ofthe bead) as occasion demands. Such cross-sectional shapes are obtainedby changing the cross-sectional shape of a tip end section of theapplication nozzle. Thus, the cross-sectional shape of the bead of thepressure sensitive sealant composition is not limited to particular one.In case that the bead of the pressure sensitive sealant composition isrequired to have a larger cross-sectional diameter or a largercross-sectional height (vertical diametrical axis in cross-section), theinner diameter of the tip end section of the application nozzle may beincreased or changed, or otherwise a farther bead of the pressuresensitive sealant composition may be applied or overlapped onto a beadwhich has been previously applied onto the surface of the base member.

The pressure sensitive sealant composition heated and applied in thestate of the bead onto the surface of the rear combination lamp unithousing is formed in a loop-shape on the surface of the housing so thatits application-starting end section and application-terminating endsection are connected. In this regard, since the pressure sensitivesealant composition heated at the temperature not lower than 100° C.,the application-starting end section and the application-terminating endsection of the pressure sensitive sealant composition in the bead statecan be molten and mixed with each other after when the application ofthe pressure sensitive sealant composition is completed, as long as thepressure sensitive sealant composition is not rapidly cool d. As aresult, the pressure sensitive sealant composition in the b ad state canbe completely stuck on the surface of the rear combination lamp unithousing without forming application defects such as a pass (clearance)in a connection section at which the application-starting andapplication-terminating end sections are connected with each other.

Otherwise, the pressure sensitive sealant composition may be previouslyheated and applied in the state of a bead onto the surface of aremovable paper or sheet which can be readily removable from thepressure sensitive sealant composition, thereby forming the pressuresensitive sealant composition into a loop-shape required for maintainingthe water-tight seal for the rear combination lamp unit. The removablesheet is formed, for example, of formed of polytetrafluoroethylene. Thethus formed loop-shaped pressure sensitive sealant composition isautomatically or manually stuck onto the surface of the rear combinationlamp unit housing of the automotive vehicle as a loop-shaped stickymolded gasket.

Furthermore, the pressure sensitive sealant composition may be formedinto the linear or string shape and wound in a required amount in theform of a coil or a bobbin. The thus formed pressure sensitive sealantcomposition is stuck on the surface of the rear combination lamp unithousing so as to be used like the molded gasket, which is notdisadvantageous from the viewpoint of ensuring water-light seal. In thiscase, the application-starting end section and theapplication-terminating end section of the linear or string shape areconnected with each other while being stuck on the surface of thesurface of the rear combination lamp unit housing at a room temperature.In this case, the connected end sections do not melt and not becomeintegral with each other. Accordingly, the application-starting endsection and the application-terminating end section are overlapped eachother by a length not smaller than 10 mm, which is preferable to obtaina sufficient water-tight seal.

Next, a method for assembling the rear combination lamp unit (with thepressure sensitive sealant composition) in the vehicle body will bediscussed.

The rear combination lamp unit with the pressure sensitive sealantcomposition of the present invention is assembled to the automotivevehicle body which has been painted. The method of assembling the rearcombination lamp unit is not limited to a particular one. Similarly toconventional techniques in which a molded gasket formed of a closedcell-type foam plastic or a butyl rubber-based adhesive is used in placeof the pressure sensitive sealant composition in the present invention,it is general to mechanically fasten the rear combination lamp unit tothe side of the vehicle body panel by using small screws provided on theside of the rear combination lamp unit. In case that the pressuresensitive sealant composition of the present invention is used forassembling the rear combination lamp unit in the vehicle body, thepressure sensitive sealant composition is interposed between the rearcombination lamp unit housing and the vehicle body panel under acompressed condition in which the pressure sensitive sealant compositionis compressed within a range of from 0 to 80% (compression rate),preferably 20 to 50% in a height of the applied pressure sensitivesealant composition (more specifically, in the cross-sectional height orin length of the vertical axis in the cross-section) of the applied beadstate pressure sensitive sealant composition. By using the pressuresensitive sealant composition under the above compressed condition,sufficient water-tight seal between the rear combination lamp unit andthe painted vehicle body panel can be obtained.

The pressure sensitive sealant composition of the present invention canexhibit high adhesiveness for the both surfaces of the painted vehiclebody panel and the rear combination lamp unit housing immediately whenthe rear combination lamp unit is assembled in the vehicle body.Accordingly, it is unnecessary to make curing for hardening the pressuresensitive sealant composition and the refore unnecessary using a curingapparatus such as an oven, for the purpose of causing the water-tightseal of the pressure sensitive sealant composition to be exhibited.Additionally, even in case that a completed automotive vehicle providedwith the rear combination lamp unit is left outside and stored in anoutdoor pool, water-tight seal between the rear combination lamp unitand the vehicle body cannot be affected by being contacted with a largeamount of water resulted from rain water or water of melted snow aftersnow fall.

Subsequently, a process for disassembling the rear combination lamp unit(with the pressure sensitive sealant composition) from the vehicle bodywill be discussed. When disassembly of the rear combination lamp unitwith the pressure sensitive sealant composition from the vehicle body isrequired, the rear combination lamp unit can be easily detached from thevehicle body panel merely by releasing the mechanical restriction due tomechanical fastening parts for the combination lamp unit against thevehicle body under usual manual operation without skill. It will beunderstood that this disassembly operation for the rear combination lampunit makes it unnecessary to use an industrial dryer or heating deviceto heat and lower the viscosity of the sealant or a removing tool suchas a plastic bar. In this regard, in the conventional techniques, usingsuch a device or tool has been necessary when the rear combination lampis disassembled from the vehicle body.

The pressure sensitive sealant composition of the present invention usedin a clearance between the rear combination lamp unit housing and thevehicle body panel is stuck on the both surfaces of the rear combinationlamp unit housing and the vehicle body panel, in which the cohesiveforce of the pressure sensitive sealant composition is larger than theadhesiveness or stickiness of the same. As a result, when the rearcombination lamp unit is detached from the vehicle body, no completecohesive breaking can occur so as to be dissimilar to the conventionaltechniques using the butyl rubber-based adhesive in place of thepressure sensitive sealant composition of the present invention. Thisdoes not allow the remains of the pressure sensitive sealant compositionto be left in an adhered state on the surfaces of the rear combinationlamp housing and the vehicle body panel. Besides, this causes the stucksurface of the pressure sensitive sealant composition to well peel offunder stress within a range of breaking elongation, thereby making aninterfacial breaking so that the sealing composition can be readilypeeled off from the surfaces of the rear combination lamp housing andthe vehicle body panel without leaving the remains of the pressuresensitive sealant composition on the surfaces.

It will be appreciated from the above, that the pressure sensitivesealant composition of the present invention can be easily detached fromthe base members (such as the rear combination lamp unit housing and thevehicle body panel), and therefore the rear combination lamp unit can bereadily disassembled from the vehicle body within a short timeregardless of skill of an operator, without using particulardisassembling tools which are required in the conventional techniquesusing the molded gaskets or the butyl rubber-based adhesive in place ofthe pressure sensitive sealant composition of the present invention.

The following examples are included merely to aid the understanding ofthe invention, and variations may be made by one skilled in the artwithout departing from the spirit and scope of the invention.

EXAMPLE;S 1, 2, 3 and 4 (1) Preparation of Pressure Sensitive SealantCompositions

A pressure sensitive sealant composition of each of Examples 1 to 4 wasprepared by supplying components in amounts (parts by weight) shown inTable 1 into a kneader and by melting and mixing the components uponheating for 120 minutes.

TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Raw Materials (parts by weight)Component A (KRATON G-1652*) 100 100 100 100 Component B (ESCOREZ 5320*)20 80 50 50 Component C (HV-100*) 150 150 150 0 Component C (HV-800*) 00 0 250 Polyethylene Wax (NEOWAX L*) 55 55 55 0 Anti-oxidant (IRGANOX1010*) 1 1 1 1 Component A Content (wt %) 30.7 29.8 28.1 24.9 *KRATONG-1652 (trade name): Hydrogenated styrene-butadiene block copolymer ofShell Chemical Co. *ESCOREZ 5320 (trade name): Hydrogenated petroleumresin of Tonex Co. *HV-100 and HV-800 (trade names): Polybutenes ofNIPPON PETROCHEMICALS CO. *NEOWAX (trade name): Polyethylene wax ofYasuhara Chemical Co. *IRGANOX 1010 (trade name): Hindered phenolantioxidant of Nippon Ciba-Geigy Co.

(2) Application of Pressure Sensitive Sealant Composition and Assemblyof Rear Combination Lamp Unit in Vehicle Body

The pressure sensitive sealant composition prepared as discussed aboveand corresponding to each of Examples 1-4 was supplied into a heatingand applying apparatus generally called a bulk melter. The heating andapplying apparatus had a casing plate heated at 150° C. The pressuresensitive sealant composition was located immediately under the heatedcasing plate and therefore molten. The molten pressure sensitive sealantcomposition was sucked up by a constant flow rate gear pump of anapplying device and discharged through a metallic nozzle onto thesurface of a housing of a rear combination lamp unit of an automotivevehicle body. At this time, the tip end section of the metallic nozzlewas set at 120° C. Thus, application of the pressure sensitive sealantcomposition was accomplished in its heated state. In this case, thehousing of the rear combination lamp unit was formed of extremely highrigidity polypropylene resin, in which no chemical surface-treatment andno application of primer were made on the surface of the housing.

The heated and applied pressure sensitive sealant composition was formedinto the state of a bead having the cross-sectional shape of a completeround having a diameter of 10 mm. The application-starting end sectionand the application-terminating end section of the bead state pressuresensitive sealant composition were connected with each other, in whichthey were immediately molten and mixed with each other to form anintegral connection section so that the pressure sensitive sealantcomposition was formed loop-shaped on the surface of the housing of therear combination lamp unit, because the temperature of the pressuresensitive sealant composition to be applied was sufficiently high. Ithad been confirmed that a seam between the application-starting endsection and the application-terminating end section could not been foundunder visual observation in case that the surface temperature of theapplication-starting end section of the bead state pressure sensitivesealant composition was not lower than about 60° C.

The rear combination lamp unit on which the pressure sensitive sealantcomposition had been applied was assembled to an automotive vehicle bodypanel which had been painted, and mechanically fastened to the vehiclebody panel by using four small screws. The paint of the pained vehiclebody panel was acrylic melamine resin paint which had been generallyused as a paint for an automotive vehicle body. No surface-treatment andno primer application were made on the top surface of the paintedvehicle body panel.

When the rear combination lamp unit was mechanically fastened to thevehicle body panel, the pressure sensitive sealant composition of the bad state was compressed in the direction of the cross-sectional height(vertical diametrical axis in cross-section). In this instance, theclearance between the vehicle body panel and the rear combination lampunit housing was about 5 mm, in which the pressure sensitive sealantcomposition of the bead state was compressed at a compression rate of50%. The compression rate was calculated by an equation ((thecross-sectional height after compression/the cross-sectional heightbefore compression)×100%)

EXPERIMENT 1) Test 1 for Evaluation of Water-tight Seal under ArtificialRainfall

Two combination lamp unite were assembled in the vehicle body of ageneral small-size sedan automotive vehicle and located respectively atleft and right parts of the rear section of the vehicle body, in whichthe pressure sensitive sealant composition (of Example 2 in Table 1) wasused between the housing of each combination lamp unit and the panel ofthe vehicle body in the above-discussed loop-shape. The sedan automotivevehicle was in a complete state. Seventy such complete sedan automotivevehicles were subjected to Test 1, so that 140 rear combination lampunits were subjected to Test 1.

In each complete automotive vehicle, the panel of the vehicle body hadbeen uniformly coated with a paint; and a portion of the panel to besealed with the pressure sensitive sealant composition did not have aso-called zero joggle joint section (jointed by spot welding) andnon-uniform panel step-section. The same portion of the panel hadleft-side and right-side parts which were asymmetric with each other.The corresponding portions (to be sealed with the pressure sensitivesealant composition) at the left and right parts of the rear section ofthe vehicle body had the same surface shape.

Each complete automotive vehicle was subjected to artificial rainfall inorder to evaluate the water-tight seal for the rear combination lampunits, as follows: A large amount of continuous artificial rainfall wasmade on the complete automotive vehicle by using an artificial rainfallmachine of the type making continuous rainfall, in which rainfall was inan amount corresponded to 20 mm per 1 hour and continued for 12 hours.After the continuous rainfall, leak of rain water into a trunkcompartment was detected by visual observation thereby obtaining testresults shown in Table 2 in which left-side and right-side lamp unitswere respectively located at left-side and right-side of the rearsection of the vehicle body as viewed from a position located rearwardof the vehicle. Evaluation of the water-tight seal of the pressuresensitive sealant composition was made with the test results shown inTable 2.

TABLE 2 Location of lamp unit Left-side lamp unit Right-side lamp unitNumber of vehicles 70 70 causing no rain water leak Number of vehicles 00 causing rain water leak

2) Test 2 for Evaluation of Water-tight Seal of Pressure SensitiveSealant Composition under High Pressure Car-Washing

Five complete automotive vehicles corresponding to those used in Test 1were subjected to high pressure car-washing in order to confirm thewater-tight seal for the rear combination lamp units. The high pressurecar-washing was conducted as follows: Water of city water wascontinuously ejected at a water pressure of 3.0 kgf/cm² for 10 minutesfrom a nozzle of a high pressure car-washing machine onto the rearsection of the vehicle body of the automotive vehicle. The distance fromthe tip end of the nozzle to the applied sealant composition was about30 cm. The amount of water ejected from the nozzle was 27.5 liters perminute.

After this high pressure water ejection, leak of rain water into a trunkcompartment was detected by visual observation thereby obtaining testresults shown in Table 3, in the same manner as Test 1. Evaluation ofthe water-tight seal of the pressure sensitive sealant composition wasmade with the test results shown in Table 3.

TABLE 3 Location of lamp unit Left-side lamp unit Right-side lamp unitNumber of vehicles 5 5 causing no rain water leak Number of vehicles 0 0causing rain water leak

3) Test 3 for Evaluation of Water-tight Seal of Pressure SensitiveSealant Composition upon Durability (deterioration) Test

In order to evaluate the water-tight seal of the pressure sensitivesealant composition upon a long time use, first five small-size sedanautomotive vehicles as same as those in Test 2 were subjected to adurability (deterioration) test. In each sedan automotive vehicle,left-side and right-side rear combination lamp units were assembled inthe vehicle body by using the pressure sensitive sealant composition.The durability test war, conducted as follows: Each sedan automotivevehicle was located in an environment test room and subjected totemperature histories (thermal cycles) in which the ambient temperaturewas changed repeatedly between a low temperature condition to a hightemperature condition. Specifically, each temperature history (thermalcycle) was such that the ambient temperature within the environmentaltest room was first gradually lowered from a room temperature conditionto a low temperature of −40° C.; secondly the low temperature wasmaintained for 83 hours; and thirdly the ambient temperature wasgradually raised from the low temperature to a high temperature of 90°C.; lastly the ambient temperature was gradually raised to the roomtemperature condition. This temperature history constituted one thermalcycle. This thermal cycle was repeated 10 times to constitute tenthermal cycles.

After the ten thermal cycles had been completed upon which theautomotive vehicle was in the room temperature condition, eachautomotive vehicle wan subjected to the same high pressure car-washingas in Test 2 under the same conditions as in Test 2. After this highpressure car-washing, leak of rain water into a trunk compartment of theautomotive vehicle was detected by visual observation thereby obtainingtest results shown in Table 4, in the same manner as in Test 2.Evaluation of the water-tight seal of the pressure sensitive sealantcomposition was made with the test results shown in Table 4.

TABLE 4 Location of lamp unit Left-side lamp unit Right-side lamp unitNumber of vehicles 5 5 causing no rain water leak Number of vehicles 0 0causing rain water leak

As a result of Tests 1 to 3 in which totally 80 automotive vehicles weretested, there was no automotive vehicle in which rain water leak intothe trunk compartment was recognized. This demonstrates that thepressure sensitive sealant composition according to the presentinvention can exhibit good water-tight seal between the rear combinationlamp unit and the vehicle body.

4) Test 4 for Evaluation of Removal Characteristics of PressureSensitive Sealant Composition

Five small-size sedan automotive vehicles (respectively having VehicleNos. 1, 2, 3, 4 and 5) as same as those in Test 3 were subjected to thethermal cycles in the same manner as that in Test 3. After the tenthermal cycles had been completed, evaluation for removalcharacteristics of the pressure sensitive sealant composition wasconducted as follows: The left-side and right-side rear combination lampunits were disassembled from the vehicle body by disengaging the smallscrews from a mechanically connecting section between each rearcombination lamp unit and the vehicle body upon previously removing trimparts located inside the trunk compartment; and then the painted surfaceof the vehicle body panel was cleaned. At this time, measurement wasmade for a time (minute) required to restore the painted surface to acondition in which the rear combination lamp was able to be assembled inthe vehicle body by using the pressure sensitive sealant composition,from a time point at which the small screws had been disengaged from themechanically connecting section. More specifically, the required timeincluded a disassembling time required for disassembling the rearcombination lamp unit from the vehicle body, and a cleaning time forcleaning the painted surfaces of the rear combination lamp unit housingand the vehicle body panel. Such measuring the time required to restorewas employed for evaluation of the removal characteristics of thepressure sensitive sealant composition for the reasons set forth below.That is, if cleaning for remains of the sealant composition wasinsufficient and difficult taking a long time, the sealant compositioncould not sufficiently and uniformly contacted with the rear combinationlamp unit housing and the vehicle body panel so as to cause leak ofwater with lapse of a long time. The test results of Test 4 on thepressure sensitive sealant compositions (indicated as “Example”) of thepresent invention are shown in Table 5 so as to evaluate the removalcharacteristics of the pressure sensitive sealant composition of thepresent invention, in which the disassembling time (minute) and thecleaning time (minute) are indicated.

For the comparison purpose, a small-size sedan automotive vehicle(having Vehicle No. 6) were prepared and subjected to Test 4 in the samemanner as that for vehicles of Vehicle Nos. 1 to 5 to obtain testresults (indicated as “Comparative Example”) shown in the Table 5. Theautomotive vehicle of Vehicle No. 6 was the same as that of Vehicle Nos.1 to 5 with the exception that a butyl rubber-based adhesive was used inplace of the pressure sensitive sealant composition. In other words, inthe automotive vehicle of Vehicle No. 6, each of the left-side andright-side rear combination lamps was sealingly assembled to the vehiclebody by using the butyl rubber-based adhesive.

TABLE 5 Example Comparative Example Left-side Right-side Left-sideRight-sid lamp lamp lamp lamp Vehicle Disae. Clean. Disae. Clean. Disae.Clean. Disae. Clean. No. time time time time time time time time 1 0.6Not 0.8 Not — — — — required required 2 0.7 Not 0.7 Not — — — — requiredrequired 3 0.6 Not 0.7 Not — — — — required required 4 1.0 Not 1.0 Not —— — — required required 5 1.0 Not 1.0 Not — — — — required required 6 —— — — 3.0 25 5.0 30 (Unit: Min.)

As will be understood from the above test results, concerning the fivevehicles (Vehicle Nos. 1 to 5), no particular tool was required todisassemble the rear combination lamp unit from the vehicle body whilecompleting a dissembling operation for the rear combination lamp unitonly within one minute, in which there was no remains of the pressuresensitive sealant composition left on the surface of the painted surfaceof the vehicle body panel and the surface of the rear combination lampunit housing. In contrast, concerning the vehicle (Vehicle No. 6) usingthe butyl rubber-based adhesive in place of the pressure sensitivesealant composition of the present invention, an industrial dryer and aplastic bar were required to disassemble the rear combination lamp unitfrom the vehicle body while requiring 3 to 5 minutes for disassemblingoperation for the rear combination lamp unit and 25 to 30 minutes for acleaning operation for the surface of the rear combination lamp unithousing and the painted surface of the vehicle body panel. Thus, Test 4has revealed that the pressure sensitive sealant composition of thepresent invention used in the clearance between the rear combinationlamp unit housing and the vehicle body panel not only can provide anexcellent water-tight seal but also can largely reduce the operationaltime required for disassembly of the rear combination lamp unit from thevehicle body.

As appreciated from the above, the pressure sensitive sealantcomposition of the present invention can exhibit an excellentwater-tight seal under environmental conditions where automotivevehicles are used, for example, in case of being employed in theclearance between the automotive vehicle body panel and the rearcombination lamp unit housing. Besides, the pressure sensitive sealantcomposition of the present invention can be easily removed from thesurface of the base members (to which the sealant composition are stuck)without leaving remains of the sealant composition on the surface of thebase members (the vehicle body panel and the combination lamp unithousing), thereby largely improving operational efficiency when the rearcombination lamp unit is repaired or disassembled from the vehicle body.

The entire contents of Japanese Patent Application P10-296798 (filedOct. 19, 1998), of which priority is claimed in the present application,are incorporated herein by reference.

Although the invention has been described above by reference to certainembodiments of the invention, the invention is not limited to theembodiments described above. Modifications and variations of theembodiments described above will occur to those skilled in the art, inlight of the above teachings. The scope of the invention is defined-withreference to the following claims.

What is claimed is:
 1. A removable pressure sensitive sealantcomposition consisting essentially of: (a) 10-40 wt % of a component Athat is at least one copolymer selected from the group consisting ofhydrogenated styrene-butadiene copolymers, hydrogenated styrene-isoprenecopolymers, and modified copolymers thereof; (b) a component B that isat least one tackifier selected from the group consisting of petroleumresins, terpene resins, rosin resins, coumarone-indene resins,hydrogenated resins thereof, and modified resins thereof; and (c) 42-62wt % of a component C that is a hydrocarbonic plasticizer, wherein saidpressure sensitive sealant composition is prepared by mixing together100 parts by weight of said component A, 20-60 parts by weight of saidcomponent B, and 150-400 parts by weight of said component C.
 2. Apressure sensitive sealant composition as claimed in claim 1, whereinsaid pressure sensitive sealant composition has a peel strength rangingfrom 10 to 50 N/25 mm at a temperature of about 23° C.
 3. A pressuresensitive sealant composition as claimed in claim 1, further consistingessentially of 6-14 wt % of said component B.
 4. A pressure sensitivesealant composition as claimed in claim 1, further consistingessentially of 25-30 wt % of said component A.
 5. A pressure sensitivesealant composition as claimed in claim 1, wherein the pressuresensitive sealant composition can be peeled off from a surface withoutleaving remains of the pressure sensitive sealant composition on thesurface.
 6. A pressure sensitive sealant composition as claimed inconsisting essentially of: (a) 10-40 wt % of a component A that is atleast one copolymer selected from the group consisting of hydrogenatedstyrene-butadiene copolymers, hydrogenated styrene-isoprene copolymers,and modified copolymers thereof; (b) a component B that is at least onetackifier selected from the group consisting of petroleum resins,terpene resins, rosin resins, coumarone-indene resins, hydrogenatedresins thereof, and modified resins thereof; and (c) 42-62 wt % of acomponent C that is a hydrocarbonic plasticizer, wherein said pressuresensitive sealant composition is prepared by mixing together 100 partsby weight of said component A, 20-60 parts by weight of said componentB, and 150-400 parts by weight said component C and wherein saidhydrocarbonic plasticizer is selected from the group consisting ofliquid paraffin, polybutene and liquid polybutadiene.
 7. A method forsealing a member, comprising: mixing together (a) 100 parts by weight ofa component A that is at least one copolymer selected from the groupconsisting of hydrogenated styrene-butadiene copolymers, hydrogenatedstyrene-isoprene copolymers, and modified copolymers thereof; (b) 20-60parts by weight of a component B that is at least one tackifier selectedfrom the group consisting of petroleum resins, terpene resins, rosinresins, coumarone-indene resins, hydrogenated resins thereof, andmodified resins thereof; and (c) 150-400 parts by weight of a componentC that is a hydrocarbonic plasticizer, thereby to prepare a removablepressure sensitive sealant composition consisting essentially of 10-40wt % of said component A, said component B, and 42-62 wt % of saidcomponent C; heating said pressure sensitive sealant composition; andapplying said heated pressure sensitive sealant composition to themember.
 8. A method as claimed in claim 7, further comprisingdischarging said pressure sensitive sealant composition through anozzle.
 9. A method as claimed in claim 8, wherein said dischargingincludes forming said pressure sensitive sealant composition into stateof a bead.
 10. A method as claimed in claim 9, further comprisingsetting said applied pressure sensitive sealant composition at aposition to be used, in which said pressure sensitive sealantcomposition is compressed within a range of not higher than 80% in across-sectional height of said pressure sensitive sealant composition ofthe bead state.
 11. A method for sealing a member, comprising: mixingtogether (A) 100 parts by weight of a component A that is at least onecopolymer selected from the group consisting of hydrogenatedstyrene-butadiene copolymers, hydrogenated styrene-isoprene copolymers,and modified copolymers thereof; (B) 20-60 parts by weight of acomponent B that is at least one tackifier selected from the groupconsisting of petroleum resins, terpene resins, rosin resins,coumarone-indene resins, hydrogenated resins thereof, and modifiedresins thereof; and (C) 150-400 parts by weight of a component C that isa hydrocarbonic plasticizer, thereby to prepare a removable pressuresensitive sealant composition consisting essentially of 10-40 wt % ofsaid component A, said component B, and 42-62 wt % of said component C;forming said pressure sensitive sealant composition into a predeterminedshape; and applying said pressure sensitive sealant composition of thepredetermined shape to the member.
 12. A method as claimed in claim 11,wherein said forming includes forming said pressure sensitive sealantcomposition into state of a bead.
 13. A method as claimed in claim 12,further comprising setting said applied pressure sensitive sealantcomposition at a position to be used, in which said pressure sensitivesealant composition is compressed within a range of not higher than 80%in a cross-sectional height of said pressure sensitive sealantcomposition of the bead state.